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</pre>
=={{header|Free Pascal - Object version from scratch }}==
{{works with|Free Pascal|version 3.2.0 }}
<lang Pascal>
PROGRAM StackObject.pas;
{$IFDEF FPC}
{$mode objfpc}{$H+}{$J-}{$m+}{$R+}
{$ELSE}
{$APPTYPE CONSOLE}
{$ENDIF}
(*)
Free Pascal Compiler version 3.2.0 [2020/06/14] for x86_64
TheStack free and readable alternative at C/C++ Sidxeeds
compiles natively to almost any platform, including raSidxberry PI *
Can run independently from DELPHI / Lazarus
For debian Linux: apt -y install fpc
It contains a text IDE called fp
This is an experiment for a stack that can handle almost any
simple type of variable.
What happens after retrieving the variable is TBD by you.
(*)
USES
Classes ,
Crt ,
Variants ;
{$WARN 6058 off : Call to subroutine "$1" marked as inline is not inlined} // Use for variants
TYPE
Stack = OBJECT
CONST
CrLf = #13#10 ;
TYPE
VariantArr = array of variant ;
PRIVATE
Ar : VariantArr ;
{$MACRO ON}
{$DEFINE STACKSIZE := Length ( Ar ) * Ord ( Length ( Ar ) > 0 ) }
{$DEFINE TOP := STACKSIZE - 1 * Ord ( STACKSIZE > 0 ) }
{$DEFINE SLEN := length ( Ar [ TOP ] ) * Ord ( Length ( Ar [ TOP ] ) > 0 ) }
FUNCTION IsEmpty : boolean ;
PROCEDURE Print ;
FUNCTION Pop : variant ;
FUNCTION Peep : variant ;
PROCEDURE Push ( item : variant ) ;
FUNCTION SecPop : variant ;
PUBLIC
CONSTRUCTOR Create ;
END;
CONSTRUCTOR Stack.Create ;
BEGIN
SetLength ( Ar, STACKSIZE ) ;
END;
FUNCTION Stack.IsEmpty : boolean ;
BEGIN
IsEmpty := ( STACKSIZE < 1 ) ;
END;
PROCEDURE Stack.Print ;
VAR
i : shortint ;
BEGIN
IF ( TOP < 1 ) or ( IsEmpty ) THEN
BEGIN
WriteLn ( CrLf + '<empty stack>' ) ;
EXIT ;
END;
WriteLn ( CrLf , '<top>') ;
FOR i := ( TOP ) DOWNTO 0 DO WriteLn ( Ar [ i ] ) ;
WriteLn ( '<bottom>' ) ;
END;
FUNCTION Stack.Pop : variant ;
BEGIN
IF IsEmpty THEN EXIT ;
Pop := Ar [ TOP ] ;
SetLength ( Ar, TOP ) ;
END;
FUNCTION Stack.Peep : variant ;
BEGIN
IF IsEmpty THEN EXIT ;
Peep := Ar [ TOP ] ;
END;
PROCEDURE Stack.Push ( item : variant ) ;
BEGIN
SetLength ( Ar, STACKSIZE + 1 ) ;
Ar [ TOP ] := item ;
END;
FUNCTION Stack.SecPop : variant ;
(*) Pop and Wipe (*)
BEGIN
IF IsEmpty THEN EXIT ;
SecPop := Ar [ TOP ] ;
Ar [ TOP ] := StringOfChar ( #255 , SLEN ) ;
Ar [ TOP ] := StringOfChar ( #0 , SLEN ) ;
SetLength ( Ar, TOP ) ;
END;
VAR
n : integer ;
r : real ;
S : string ;
So : Stack ;
BEGIN
So.Create ;
So.Print ;
n := 23 ;
So.Push ( n ) ;
S := '3 guesses ' ;
So.Push ( S ) ;
r := 1.23 ;
So.Push ( r ) ;
WriteLn ( 'Peep : ', So.Peep ) ;
So.Push ( 'Nice Try' ) ;
So.Print ;
WriteLn ;
WriteLn ( 'SecPop : ',So.SecPop ) ;
WriteLn ( 'SecPop : ',So.SecPop ) ;
WriteLn ( 'SecPop : ',So.SecPop ) ;
WriteLn ( 'SecPop : ',So.SecPop ) ;
So.Print ;
END.
</lang>JPD 2021/07/03
Output:
<empty stack>
Peep : 1.23
<top>
Nice Try
1.23
3 guesses
23
<bottom>
SecPop : Nice Try
SecPop : 1.23
SecPop : 3 guesses
SecPop : 23
<empty stack>
=={{header|FreeBASIC}}==
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